Thermionic-tube circuits



July 24, 1928. 1,678,077

W. T. POWELL THERMIONIC TUBE CIRCUITS Filed Sept. 17; 1924 AMPLWWER 3. Fla-'2 INVENTOR WINFR'ED T. POWELL.

ATTORNEY Patented July 24, 1 928.

. UNITED STATES PATENT OFFICE.

wmrnnn r. POWELL, or noonEs'rEa, NEW YORK, assronon m 'rnE s'rnommno- OARLSON TELEPHONE morac'runmc comm, or aocnEs'rEa, NEW YORK, A

CORPORATION 01' NEW YORK.

TEEBHIONIG-TUBE CIRCUITS.

Application. filed September 17, 1924. Serial No. 788,206.

This invention relates to amplifying devices and more particularly to such devlces in which thermionic tubes are emdployed.

It has been noted that radio evices o 6 crate more satisfactorily if the control 'e ement or grid is maintained at a certain difference of potential with respect to its filament. In obtaining this result, small sized batteries have been employed .which arevices.

the use of a selenium cell forgmaintaining the properdifl'erence of potent1a1 on one o the elements of a thermionic device.

will a pear from the description and appende claims.

In the drawings Fig. 1 represents a radio receiving set includin an antenna, a detector device with its contro circuits and an amplie fier device of the vacuum tube t pa in WlllCh a photoelectriccell is connecte to the grid of the amplifier. Fig. 2 shows a modified form of the amplifier in which several photoelectric cells are connected in series and are energized by a lamp, lighted by alternating current. It will be understood that the amplifier of Fig. 2 may re lace the am lifier appearin at the right 0 the dotted line of Fig. 1. Fig. 3 shows still another modification of. the present invention in which the photoelectric cell is enclosed within the evacuated envelope of the amplifier tube, so that it is energized from the light of the fila 1 to cooperate with the detector; arrangement of that figure. p a

' Referring especially to Fig. 1, 5 designates an antenna which is inductively coupled to a tuned input circuit 7 of-a three-element do tector or thermionictube 8. This input circuit includes the grid condenser 9 and well known grid leak 10 in series with the con- 20 and one side of the filament lighting cir- More specifically this invention resides in Other specific features of this invention :of the filament 14. .45 ment. The amplifier of Fig. 3 may likewise be substituted for the amplifier of Fig.

also connected to one side of the filament- 24,

which is lighted from the filament battery 25. The output circuit extending from the plate cuit is inductivel coupled by a transformer 21 to the input circuit of the amplifier tube, generally designated 12. This input circuit includes a photoelectric element 26 and is connected at one point to the grid 13 and at its other end to the filament 14 through battery 15. This hotoelectric element may be in the form 0 a olarized selenium cell, which is capable of eveloping a difference of potential under the influence of light. A particular type of selenium cell which is effective for the purpose specified, is known as the Fritts type, described in chapter 2 on page 16 of the treatise, entitled Selemum cells, by T. W. Benson.

This cell is formed'by melting selenium directly on a copper plate and pressure is then a plied so that the soft selenium enters into c lemical combination with the copper and adheres firmly thereto in the form of a thin film. When the selenium film is cooled, gold leaf is applied thereto. The gold leaf orms one electrode and the copper plate the other electrode of the cell. Suitable protectmg strips serve as a mounting frame and a sheet of ver thin mica serves as a protection to the gold oil'surface.

The filament of the amplifiertube is lighted from a source of A battery 15, regulated b a rheostat 27 This battery serves to .li h the lamp 28 and its light is focused on t e selenium cell by the lens'29. The rheost-at 27 provides means for varying the intensity of light from lamp 28, so that any desirable amount of difference of potential may be applied to the grid 13. The output circuit of the amplifier including the receivers 16 extends from the plate 30 to one side in the receivers 16. The photoelectric cell -26 applies such a negative potential to the grid 13 of the amplifier with respect to its filament that it functions without substantial distortion.

The amplifier of Fig. 2 is substantially similar to that of Fig. 1 and may be substituted therefor, by connecting the portion of the detector at the left of the dotted line, at points 17 and 18 to the conductors 19 and 20 of Fig. 2. Inthis modification several photoelectric cells, 26', 26, 26 and'26 are connected in series. A source of alternating current 31 serves to light the lamp-28 and the lens 29 concentrates the light on the several photoelectric cells.

y In the modification shown in Fig. 3, which may replace the amplifier of Fig. 1, the photoelectric cell is enclosed Within the evacuated envelope of the amplifier tube together with the filament, grid and plate elements. The cell is so positioned that the light from the filament affects its functioning to produce the desired diiference of potential on the grid 13.

While the present disclosure shows one or more photoelectric cells replacing the socalled 0 batteries, it will be understood that the present arrangement may be used to replace other batteries in the circuits of detector and amplifier devices.

What I claim is:

1. In an amplifier-device, a thermionic tube including a filament, a plate element and a controlling element, an input circuit connecting said filament and said controlling element, an output circuit connectingsaid filament and said plate element, heating current for said filament, and a light controlled unit for developing a difference of potential between one of the elements of said thermionic tube and said filament proportional to said heating current.

2. In an amplifier device, a thermionic tube including a filament, a plate element and a controlling element, means for heating said filament, an incoming circuit connecting said filament and said controlling element,

an output circuit connecting said plate element and said filament, and a photoelectric unit energized by said filament for developing a difference of potential between one of the elements of said thermionic tube and said filament. v

3. In an amplifier device, a thermionic tube including a filament, a plate element and a controlling element, enclosed within an evacuated envelope, an input circuit connecting said. filament and said controllin element, an output circuit connecting said filament and plate element, and a photoelectric unit within the-envelope of said thermionic tube for developing a difference of potentialbetween one of the elements of said thermionic tube and said filament.

4. In an amplificgdevice, a thermionic tube including a filament, a plate element and a controlling element, a source of heating current for said filament, an input circuit connecting said filament and said controlling element, an output circuit connecting said filament and said plate element, and a photoelectric device for impressing a potential upon the controlling element of said thermionic tube more negative than said filament, said potential being proportional to said heating current.

5. In an amplifier device, a thermionic tube including a filament provided with two terminals, a plate element and a controlling element each having a terminal, a source of heating current connected to said filament terminals, an input circuit connecting a filament terminal and said controlling element terminal, an outputcircuit; connectingone of said filament terminals and said plate element terminal, and a photoelectric device WINFRED "r. POWELL. 

